As much as I like to keep things original, I have to admit...I've had 2 Bronco 2's, I've carried a passenger in the back seat of my 88 Bronco 2 once...had 2 other people with me, so one had to ride in the back seat...he said there was plenty of room, the downfall is trying to get in and out of the back seat is a PITA....luckily the 2 passengers were teens so they're young enough and flexible enough to get back there and get back out...I'm only 39 and its a pain for me getting in and out of there and I'm only 6 feet tall and pretty skinny....the back seat in my current Bronco 2 has been folded down the past couple of years; I just carry a small tool kit, a bag with my trailer hitch and adapters in, and a few other things...mostly just use it for cargo space anyways. So I could see taking the back seat out would be nice for most people, and you'd probably free up 50 or so pounds of cargo capacity and have more room for other stuff besides....although I'm not sure what it looks like with the seats removed, with the seats folded down you have a nice flat area for storage, I think if you take the seats out you'd have to build it all back up to get a flat cargo area again, then again it would depend on the usage of the area that you have planned. I just keep the seats folded down and pretty happy with the space I have to haul stuff, the carpet in mine is trashed so throwing greasy, dirty stuff back there doesn't bother me...previous owner had a dog, or dogs so the carpet is pretty well destroyed. I thought about doing a restoration, but after just the engine/transmission fiasco the rest of it can stay as is, I may try and paint it at some point but it'll get painted 1 solid color, none of that nonsense 2 tone crap like it is now. Just haven't done it because I don't have the patience for doing the prep work involved LOL.
You don't have much in the way of headroom in stock form either, so trying to build anything up inside for storage is pretty limited if you wanted to do a storage build and then use the top of that for a sleeping area, I'm not sure I'd fit back there, maybe laying at an angle I've never tried it....I was able to in my Jeep, but not sure I'd fit in the Bronco 2...I think I'd prefer a tent at that point anyways LOL.